The present invention relates to a resin-coated mount substrate constituting, for example, an electronic circuit of an electronic controller mounted on a car, and relates to a method of producing such a resin-coated mount substrate.
A resin-coated mount substrate is configured such that a substrate unit in which various electronic parts are mounted on a printed substrate is resin-coated with a sealing resin material for the purpose of performing waterproof, moisture-proof, corrosion-proof, and/or heat release, etc.
Conventionally, such a resin-coated mount substrate is produced by the following method.
A resin-coated mount substrate 100 shown in FIG. 4 is disclosed in Japanese Patent Unexamined Publication No. Sho. 60-54457. The substrate 100 is formed in such a manner that electronic parts such as a resistance 102, a transistor 103, and a microcomputer 104 are mounted on a printed substrate 101 to constitute a substrate unit A, the substrate unit A is attached in a casing 110, and then a sealing resin material 111 is injected into the casing 110 and hardened so that the substrate unit A is buried in the sealing resin material 111. The resin-coated mount substrate 100 is used as it is in the state where the hardened sealing resin material 111 and the casing 110 are integrally formed with each other, and the casing 110 is used as an exterior casing as it is.
Alternatively, the resin-coated mount substrate 100 may be formed by using a tray-like casing for injecting sealing resin in place of the casing 110 used as an exterior casing. In this case, a tray-like casing and a sealing resin material are integrated with each other and the thus obtained integrated member is accommodated in a further separately prepared exterior casing for practical use.
Various techniques similar to the resin-coated mount substrate 100 are disclosed in Japanese Patent Unexamined Publications No. Sho. 59-112700 and No. Sho. 60-17990; Japanese Utility Model Unexamined Publications No. Sho. 60-11475, No. Sho. 60-94882, and No. Sho. 61-134082; etc.
Further, a resin-coated mount substrate 200 shown in FIGS. 5(a) and 5(b) is formed in such a manner that a substrate unit B in which various electronic parts (not shown) are mounted on a printed substrate is set into an injection mold 201, and thereafter a sealing resin material 202 is injected into the injection mold 201 and hardened so that the substrate unit B is buried in the sealing resin material 202 (see FIG. 5(a)), and then the hardened sealing resin material 202 is released from the mold 201 (see FIG. 5(b)). The resin-coated mount substrate 200 is accommodated in a further separately prepared exterior casing for practical use.
One problem with the resin-coated mount substrate 100, however, is that when the casing 110 is used as an exterior casing, a large the quantity of the sealing resin material 111 must be injected into the casing 110 increasing the weight. Additionally, in the case of performing molding by using a tray-like casing for injecting sealing resin, the exterior casing is increased in size to secure a space for accommodating the tray-like casing.
The resin-coated mount substrate 200 can solve the foregoing problem with the resin-coated mount substrate 100. The substrate 200, however, has a problem with adhesion between the sealing resin material 202 and the injection mold 201, even in the case where a mold releasing agent is applied. This adhesion makes mold releasing troublesome and there are concerns that stress applied to the substrate at the time of mold releasing will generate a crack in the substrate or damage the conductor portions. As a result, the workability and reliability is poor.